CA2057017A1 - Master for optical element replication - Google Patents

Abstract

A master for the replication of optical elements is prepared by the steps of a) focusing an information modulated energy beam on a phase-change optical recording layer so as to form a pattern of two different phases in said layer corresponding to said information; and b) selectively etching away one of said two different phases so as to form a relief pattern corresponding to said information. The master so made can be used directly as the stamper in the injection molding process or the 2-P process for the replication of optical elements.

Description

Wo~/00598 2 ~ ~ 7 ~ ~ 7 PCT/~S90/03500 . , MASTER FQR OPTICAL ELEMENT REPLICATION
~ield of the Invention The present invention i~ directed to a method for forming the ma~ter that i9 u3ed in the replication of optical elements and the ma~ter itself. Also tiscio3ed i~ a method for replication that u~es the master of the inve~tion as the stamper.
DescriptioDL~la~i~e to the Prior A~t It is well known in the art to form an optieal element containing large amounts of information. Video disks and digital audio disks are typical optical elements. It is readily apparent that there i~ a need to be able ~o easily and cheaply replicate these elements.
Conventionally, optical disk~ or disk ~upports are replicated u~ing either the injection molding proce~s or the 2-P ("2-P" i~ a i~horthand reference to ~hoto~olymerizatio~ ~rocess. In these proce~ses, a ma3tering disc in the form of a photoresi~t coated glà s disc is first exposed with a modulated lasër beam 80 that, after photoresist developmènt, the desired information i encoded into the photoresist^layer in the form of a relief pattern of pit~ and/or grooves. Since the exposed and developëd photores~st càn not be ù~et directly, thiQ
master disc must then be metallized to provide a conductive surface for a following nickel elec~ro-pla~ing process. The ~ickel plated layer is peelet off from he master di~c to form what is 30 ~called a ~tamper. A~center hole is then punched and the out~ide di~meter i8 trimmed to the desired dimensions and the back ~urface i8 polished so that the stamper can ~it in~o the injectio~ molding 7 I f l ~ P~ ~f It.~ç~
machine or the 2-P mach;ne to perPorm the replication .

', WO 91/00598 ~ D ~ 7 ~ ~ ~ PCT/US90/03500 One problem with this process is that the photore~ist layer used to form the master i~ only sensitive to W radiation. This necessitates the use of ga~ ~V la~ers ~o form the informatio~ pattern in 5 the photoresi~t layer. These lasers are expensive, I
bulky, and difficult to control. They have to be~ 1, mounted separately from the optics necessary to focus them,' making alignment costly and difficult.
Another problem~is that the absorption'of thé laser beam by the photoresist layers is not very efficient. As a re~ult, the laser exposure step has to be carried out at relatively slow ~peed, limiting the throughput of the process.
' Ano~her problem i~ that the photoresist layer tends to ~well during sub~equent de~elopment steps. This can limit the resolution and useful packing de~sity of recorded i~ormation. This àlso 'complicates the replication process when fine control of replicate feature dimensions is needed.
Another~problem is that the ~tamper making process i8 complicated. It involve3 metalizing, electro-plating, polishi~g, peeli.ng, punching, and ~!' i '~'ri''mming.`''As'a'''re'sult; 'the''équi~imë~t'~is'"é`x'p'ënsive, the yield is'io'w and the'process i~ timë consuming.
The art relating to proces~es for replicating optical elements is extensive and only a few of the many patènt~ will be nentioned here. I~
United Statè~ iàtënt 4,7Z4,043 i~sued Fe~'ruary'9, 1988 there' i8 disclosed a method wherein the gla ~upport for the ma~ter 18 flr~t coated with a layer of an oxlde or ~itride. Otherwise; the process is conventional and has all of the difficulties ., ) ;3 i ~ 3 ). ~ , .. . ~? . ~ :r . / :. ' Y \ . ~r : .. ;
discu~ed above. In United States'Patent 4,650,7~3 ' !~.C;~ O 5 ., ,/ f, i ~ ~ " ~ J
assued March 17,~1987, there i8 described another 35 recent method u~ing a photore~ist to form the ma~ter. ' r. '~ '? 1 o 1; ri ~ " ' W~ 91/0059~ 2 ~ 5 7 ~ 1 7 PcT/us9o/0350o ,. . .. .

In United States Patent 4,565,772 there is described a radiation sensitive material which, after exposure to a modulated laser beam, can be used directly as the'stamper. The radiation sensitive material is a complicated multilayer structure. It relies on a radiation sensitive layer which discharges gas when irradiated with laser energy, thereby causin~ a deformation in an overlying metal -layer. ` ~ '' Thus, there continue5 to be the need for a method for replicating optical elements where the mastes does not need to be formed u~ing a photoresist. The method should be simple and should be rapid, thereby increasing the reliability and throughput for the-process.
Summary of the Inv~n~ion ' The present invention 'represents a radical departure from the'conventional methods for making the master for optical element replication. No photoresist is used. Ins~ead, a phase-change optical recording element i~ first exposed so as to form a pattern in 'the recor'ding layer as would:be ''^-conventional ~or this type of element.'' Thus, for : example, a pattern of crystalline"areas' i8 formed in a'layer that i's'otherwise amorphous'`or-a pattern of--amorphous material' is~~ormed~in'a'layer:that is '' otherwise crystaIline.J~The~ the-mastér is ~ormed by - -~s`ele'ct'iYely etching~~either~the amorphou~ area~'or the crystalline'area~'thereby f'ormi'n~g`~the-desi-red`relief 30i pat~ern~"on"`'the'surfàce bfi'~he ma~ter.' '~' "'- Thus,-in''accordance;with one''aspect'~of~the ~i7 ~invention,'there`;is provided;a^met~od'`for'~orming a ~'~'~~'master' for:making rèpI'i:ea`teioptic'al~'~e'ieménts~,i said :~ '; method-:compri 8 ing'~t~e 8'~epg'~'0f~ 3 t~ 2 35~ r~ -3;r~?~ r~rl3 -;.~ ?.~l,r ~ -} i~

WO91/00598 ' `` P~TtUS90/03500 2~7~7 _4_ ~
a) focusing an information modulated energy beam on a phase-change optical recording layer so a~ to form a pattern of two different pha~es in said layer corresponding to said information; and b) - gelectively etching away one of said two .
di~ferent phaseY 80 ag to form a relief pattern corresponding to said information.
In accordance with another aspect of the invention, there is provided the master produced by l0 the above method~ !
.In accordance with anothex aspect of the invention, there is provided a method for making a stamper ~rom said master including the additional steps of plating said relief pattern to form.a stamper layer and then removing said stamper layer from the surface of said master.
.-In accordance with yet another aspect of the invention there i8 provided a method for replicating optical elements using the master described abo~e as ~0 the stamper.?.
; ; Other aspects of the invention will:become clear fromLthe following detailec1 description.-".--~rie~ ~escription o~ the ~rawi~g~ - ^
.- - - In_Figure .l.there is illust~ated.a schematic 25...repregentation of the method o~ forming a master accoxding to.-,the present-inventio~
~ Figure 2 is arphotographjof~the:surface of a i!~;i ~replica di~8~,made using~the~ma~terJo~ ,the~inventi v~3~.iDetailed Dei~c~iption of,~he-Invention~
30Opticaljeleme~ts are-~most~commonly~.produced -~ the-~f~rm o~ a~di8k.fjP~oweverjia~will be ~,appreciatedj.i,the~,~replication method-c?f th.e~invention 8 niot~limited~,to~thi 8,j'~0rm .0~ eleme~t.~Other;forms, ~uc~ as for example~cr.qdit card~shaped,l1elements, are also contemplated. For convenience, the replication W~91/0059~ 2 ~ ~ 7 0 ~ 7 ~ PCT/US~0~03500 f ..
--5-- , of disk~ will be described in detail with the understanding that adaptations to other forms can be easily accomplished by tho~e skilled in the art.
The current invention provides an improved method for forming the master for making optical element~. This method utilizes phase-change optical recording layers to replace the photoresist layer in the conventional mastering method! ,The phase-change layers are typically sensitive to the radiation of diode lasers. Therefore, the use of troublesome gas lasers can be a~sided. The ~ensitivity o~ the layers to energy induced phase-change is usually very high.
~he speed of the exposure step can therefore ~e.
greatly improved compared to the proce~s using photoresi~ts and UV la~er~.
The problems associated with the swelling of the photore~ists usually u~ed to make the master are eompletely eliminated In the process of the invention, the master ean be tested at various stage in it~ preparation to '' insure 'successful eompletion,of previou~steps.
Thus, the proGess.can,be,re~tarted.~before,the di~icult 6tamper plating and peeling steps are attempted thereby reduci~ng wasted,~effort.~ For.
example, the information in ,the pha~e-change layer can be confirmed'before and after the etching step.
,The adhesio~ of the pha~e-change~recording materials'to the ~upports on which they.are,~coated is excellent. In addition, the phase-change material~is 30 'a,metal alloy and i~ therefore very.,durable. .It is ' much more durable, for example9..than exposed and developed photore~ist. Thus,the master of the invention can be u~ed directly a~.the stamper~r ellminating entirely the,need.~or making.a ~eparate stamper, for example~gby;~ickel~plating~ ~; ? ~

.. . .

`'' '' PCI/US90/03500 --6~
The ability to u~?e the master of the invention as a stamper in the replication process is a significant advantage of the invention. This feature makes it economically feasible for the first 5 time to make only a few hundred replicates. In the prior art process, the extremely high cost of forming the nickel stamper had to be distributed over a very large number of replicates so that the cost per - replicate could be rea~?onable. In fact, the speed.
and ease of making the present''master makes it economically feasible to simply make additional masters whe~e up to several thousand replicates are needed. Of co~rse, the ease of making the present master is also an advantage even where nickel stampers are needed for extremely long production runs.
- ' The present invention utilizes the -- difference in the etching rate'for two different phases of the same alloy. Where two different phases are formed, therie will almost always be a difference in the etching rate. Thus,'any phase-change optical recording material can be used i~ the present '~
invention.~'Usuaily,~'the~two'phai3e~? that'are usëd for phase-changëSoptical recording à:ré thè amorphous phasë and ~he crystalliné'phàse; ~Etchants;,can be found for thése`matèrials'that preferentially etch the crystalline'phase and either do not ëtch the !~amorphous`phase-or etch the amorphous phase at a much - ~''Si~we~'rate~ "c~r2 ~i~L ~ r~
.,30.. !~ ` Thu~';'it is preférred to ~orm t~ë mastèr of the in~ention'by'providi'n~'a amorphous pha~e-change o'ptical'rècording iayër'"`and'~rec3rding thë'information in the~for~f'crystailine mark? and/or gro'ove~~in r;: ~ ~ r -, ~ ~ r ~ ?~ J ~' r the amorphous'layer'.~"The'crystailinë`màr~ arë then 35;ip'r'èferént'iaiiy e'tchëd?/so'~'as to'iiea'vé the7'~e's'ired ~? ~'- ' `~ -- ; r; r .~ . ? ... ~ S O .~ 't ~" -~ ,-r~
relle~ ~n~the-surface of-the"master.

WO91/0~98 ' 2 0 .~ 7~ 1 7 P~T/US9o/03500 The method of the invention is illustrated in schematic Figure 1. In Fig la, there is shown a phase-change optical recording element before exposure. The element comprises a support 10 having thereon a phase s change optical recording layer 20. Fig lb illustrates the element o~ Fig la after recording. The layer contains unrecorded portions of amorphous material 22 and recorded portions of crystalline material 24. In Fig lc, there is shown the element after etching. The o crystalline portions 24 in Fig lb have been etched away leaving amorphous portions 22. The resulting element can be used as a master or stamper as`described herein.
The present invention is not limited to etching crystalline areas. For some materials, the 15 amorphous areas may be preferentially etched. Other materials, such as those~found'in ~uropean Patent Application 018445Z;record information as the difference ~etween two different crystaline phases.
Preferentially etching one'of these phases to form a 20 master would therefor~ be within the scope of the present invention.``" ' - ' The selection'of the'phase-change recording material is~not~critical'.' Uséful phase-changè optical recording'materiàls for use in the presént invëntion "'àre'described, for èxample, in: ' ''' .,, - i . . -~ . - -;-- European'Patent Application 301240.3, filed 15 February-1988 by Pan,'Tyan'and'Préuss (antimony-tin and ` antimony-tin~;and~~indium)','~~''' '' U.S.' Pàtents'4,795,695',' issued 03'' January i989 and '-4,812,~386,~'issued~14 March`1989 by Pàn;~'Tyan and Marino c ~ 7 ~ t Lr -' (antimony-tin and germanium);
~'U.'S Patents i',798,785, issuèd 17 January 1989 and ~ C~ j r~ L ` ~ J . . ~
r ~-4,865,955, issued 12 September 1989,byl Pan"Tyan and Vazan (antimony-tin~'and aluminum~;

WO9l/00598 2 0 ~ 7 0 ~ 7 PCT/US9D/03500 ' ' ' '' -8- l"'-' U.S. Patents 4,774,170, issued 27 September 1988 and 4,812,385, lssued 14 March 1989 by Pan, Tyan and Preuss (antimony-tin and zinc);
European Patent Application 114636.7, filed 08 s August 1989 by Pan, Tyan, Vazan and Preuss (antimony-tin and various third elements?;
PCT Application 04975, filed 13 November 1989 by Tyan, ~aychaudhuri and Vazan (antimony-tin-indium and a ~ourth element); and PCT Application 05435, filed 07 December 1989 by Pan, Tyan and Vazan; (antimony-tellurium).
Other useful optical recording phase-change materials include germanium-tellurium alloys, particularly those containing aluminum, titanium, tin and antimony. These 15 phase change optical recording materials are particularly suitable because they~have high sensitivity to diode laser radiation, are chemically stable, and form crystaline marks wlth well defined boundaries. These materials are employed in the form ~o of continuous thin films with a thickness of from about 100 angstroms to about 2000 microns.
The selection of the particular etchant is also not critical. The etchant~is chosen so~as to preferentially etch one of the phases in the phase-change material. In general, these etchant~solutions consist of acids, bases or acidic or basic oxidizing species in a suitable solvent. Specifically,jthese etchants inolude concentrated hydrochloric acid and its dilutions, with water, down to O~ Ol,4vol% i concentrated sulfuric acid and its dilutions,,with water,,down ~o about 0.01 vol%; oxalici acid solutions~in waterjwith a concentration~range of aboutj,0.0i wt~ tolfl2 wt%;
(NH4)2S2O8 solutions in water with a concentration range of about`O.01 wt% to 12 wt%, Na2Cr207 solutions in WO91/00598 2 ~ ~;7 017 pcT/usso/o3soo water with a concentration range of about 0.01 wt% to 12 wt%; K3Fe(CN)6 solutions in water ~ith a concentration range of about 0.01 wt% to 12 wt%;
pota3sium and sodium hydroxide solution~ in water with a concentration range of about 0.01 wt.X toO -about 12 wt%; ammonium hydroxide solutions in water W9 th a concentration range of about 0.01 wt.% to ..about 12 wt%. Any combination of,,two or more of the ~ove etchants is al~o u~eful.
For improved wetting of the phase-change optical recording layer by the etchant and more uniform etching of large areas, a suitable surfactant may be added to the etchant in an amount sufficient , to obtain useful wetting properties. Useful surfactants include, but are not limited to, polyoxyethylene,ethers,3uch as those sold under the TritonT'Y mark (for example, TritonTM X-100 and TritonTM N101), or under the Nonidet or ~rij tradenames (such as Nonidet P-4~ and Brij 35), polyoxyethylenesorbitan deri~atives,such as those-sold under-the Tween tradename (for e~ample Tween 20 or~,Tween,,40),,~ and ~po~yglycol, ethers such as those ;. sold under the Tergitol tradename-(for example .,~, Tergitol NPX and Np-7),,,v Otper useful ,surfactants 25 --include,~luorinated surfactants such as those sold ,under the,Fluor~dTM, mark:such a~-Fluorad-FC-99.
7;j~", ,,, ,"It was~observed that the-extent of sur~ace oxidatio~;of thei,amorphous.film7and~o~the laser cr~stallized~m,arks,;affected-ithe etching rate,. -As a 30 ,-,result,-~the,~optimum,etch~-duration depends;on,the storage,ti~e.and"~,stosage enviro~ment of the.alloy film;~.~,Etching~of_~reshly,lwritten,marks in freshly pr,epar,ed~alloy5~ilms~isithe,~preferred embodiment of -~X~ thi8~,iIlV~entiOn. o~ f ~ 3,J .L~ .3s,-, ~ c;

wo9l/ooss8 ~a~ PCT/U~90/03500 The etching ~tep is carried out in a conventional manner. An exposed phase-change optical rècording layer can be immeri~ed'in the etching bath , ' ox the etching bath can be sprayed on the exposed surface. It is'`pre~erred`to immerse the layer in the etching'bath and spin the layer during etching so as to promote uniform etching.
: The master formed by the described p'rocess is another a pect of the inve~tio~. Th~s-, ~here is provided a master for making replica~e optical elements, said master comprising a support having thereon an etched phase-change optical recording layer having a relief pattern corresponding to to the information that is to.be transferred to said optical lS element. '' - Because of the e~cellent`adhesion of our selected phase-change layers to glass, and the good abrasion:resistance of the materials, a glass support master can be used directly as a stamper for reproducing information by pressing into contact with an appropriate polymer 'a in the 2-P proceYs. This ~'greatly s`impl'ifies~the stamper:makingiproces~
~ ' Photopolymerizable'polyme'r:composit'iong that `-'are'useful in'thi~ embodiment are well known`-'in the 25.-iart and are described,--for example in U.S;'Patents 4,729,938;'4,296,~158;'4;'312:,823'and-4,668,SS8.'': A
-~ particuIarly'preferred oomposition~is as follows:
~hexanedioi'"diacrylate~i(40-..parts~by weight);~
:~ 3~';pentaerythritol triacrylat'ei'(20lparts~by~weight~;
30 *CelradTM'~3200,~a~diacrylàt'ed':'epo~y'~`oligomeriifrom ' h:Interèz Inc'~(40-~~parts by'weight)'and~DarocurTM
Yi"?ll73 an aromatic`'ketone photoinitiator~from;`iEMi:
~C `t`ITldU8trie9',~InC r~ Thi~ i5 referred'to-!in~Example 9 a~d iE the material used to make-the~i2epl~catë~shown 35 in Figure 2. '`J~

W~ 91/005g8 2 ~ ~ 7 ~ ~ 7 Pcr/US~/03500 The master of the invention can also be used in the production of nickel stamper~ for optical disk replication and/or support production. The etched phase-change master can be thPrmally or flash S crystallized. Itican also be conductively coated, electroplated with nickel and~the nickel replicate polished, peeled, punched and tximmed to obtain a nickel stamper in the conventional manner.
As noted ~bove, the masters of the invention can be used directly as stampers in the 2-P process.
They can also be used directly in the injection molding process.` In this embodiment, it is desirable ~o initially coat the phase-change optical recording material on a durable support. Suitable supports may 15 --include ~blank" nickel stampers, polished stainless steel and structural polymers.
- Polymers that can be used in the injection molding of replicates are conventional. Useful polymers include poly(vinylchloride); copolymeric vinylchloride vinylacetate; polycarbonate-resins;
poly~methylmethacrylates); and polystyrene.
Preferred examples include Mobay MarkrolonTM
DP-1-12-18`polycarbonate ! ànd-Tey:ln PanlitèTM AD5503 .,, .. .. ~ . ~... .... .. .. ... .
polycarbonate-.- -- - -~ Opticalirecording;layers can be prepared by - conventional'thin~film deposition techniques such as ~F (radio freque~cy) and DC:<dirëct current) ~puttering from an alloy target u~ing the alloys of Ithe;invention~ :iEnha~cement of-sputtéring processes by applying;magne~ic~!fields~S(magnetron-sputtering) can also be used. The thick~ess o~ the films can bè
- ~~rom~laifew tensito a few~hundréds of nanometers depending;on`compromi 8 ès`~among fàctors such às contrast,i'~sensi~ivity,; piodu`ction rate~9Lmat`e~r'ial 35 C08t`, ea~e~o~ ~controlr ~dàta;rate, etc.

';
., .

WO9l/00598 ~ PCT/US90/03500 ~ upports which can be u~ed include plastic plates, such as polyethylene terephthalate, polymethyl methacrylate, and polycarbonate, a glass plate, paper and metallic plates such as aluminum.
As noted above, where the master is used directly as a stamper in an injection molding process, the support i~ preferably a durable material.
~ Recording information on the thin film lay~ers made using the,alloy of this invention is achieved ~y ~ocusing an in~ormation modulated laser beam on the layer thereby forming a pattern of information on the layer in the form of cry~tallized areas in an otherwise amorphous layer.
During recording, the recording material is typically spun at a constant rate, e.g., 1800 rotations per minute (rpm) or at a,rate that changes as a function of the recording spot radial position.
A track of information is recorded on the optical recording layer in the form oP selected crystallized area8 as a result of localized exposure to,the ~
modulated recording~beam. As recording continues, .. . . ..
,their'ecord~ng beam~moyes,radiallyjacross..the ~., recording material~ thereby causing information to be recorded along a spiral,or concentric track. The :
- - . - - - - - -25 ,sizes and,spacings o~ the information encoded marks vary in accordance with the information content~of the recording laser,drive signal, ,,.-~ .`~'1!''.' j, ',,'', 'Yi~2~'~ I'''t j ~The,~ollowing,examples are-ipresen,ted,f,or a (~,further~unders,tanding,of,the~invention.,,~
30, xam~le l.dJ ~,3 ~,. 3,~ J
-r~, t.~ ~ -rl ~; thin-f~ilm" about ?- ~m,~n,thickness on a gla88 support,~of Sb-Sn~In alloy,l,with atomici ~, compo~ition.of 60~/o~25/~ 15% was prepared by ,-.
RE-sputtering; The~argon pres~ure used,jin th~e~
~puttering process wa8 about 13 mTorr, and the RF

WO91/00598 2~7~7 PCT/~S9~/03~00 , .
-13~
power was about 1.5 Watt/cm2. Crystalline spots and tracks were then ~ritten onto the disk while the disk was spinning on a spindle, using a focused 830 nm diode laser beam through a 0.55 NA objective.
A solution of 0.1 wt% oxalic acid in water . . . " , was freshly prepared as etchant. The disk was immersed in the etchant for 50 seconds while the disk was spinning. The disk was then rinsed in distilled water. The disk wa~ i~ub~equently dried by spinning at high ra~e. The disk was then examined by optical microscopy and scanning electron microscopy (SEM).
It was found that the laser crystallized spots and tracks were completely etched away and the boundaries were well defined. The amorphous area was only slightly etched. This etched disk wa~ then ready to .
be used as a master or as a stamper.
Example 2 A thin-~ilm about 70 nm in;thickness on a glass support, of Sb-Sn-In alloy with atomic composition of 6070 - 25Zo - 15% was-prepared and laser-marked as in Example 1~
.A solution.of 1.0 vol% hydrochloric.acid in water was freshly prepared as etchant. The disk was immersed in the etchant for 240 Eecond~i while the disk was spinning.~ The~disk was~then rinsed in ~.
,, .. , .. ,, .. ~ . .. , .. , . . , , ,, .. ,. ~ .. .. . .. ..
distilled.water. The dis~,wa~ subsequently dried by ,~ spinning at high,ra~e..~ ,3 ;. "~...." j ` ~
~ , The ti~k was~then examined.~by,.optical microscopy.and SEM. ..It.was.~ound.that the;laser .crys~allizedi.spots~-and ~tracks wese1completely etched . away andithe bou~daries were.welljdefined. The amorphou~ area wa3 only slightly etched.!iThis.etched disk wa~ then.ready,.~o be used.asr,iafmaster or as a Wog~/OO~g~ ` ,; ; : PCT/US90/03500 f~
2~ 7~ 7 -14-~xample 3 A thin-film about 70 nm in thickness on a glass support, o~ Sb-Sn-In alloy with atomic composition of 60%-25r~ZJ-15% was prepared and `laser-marked as in E~ample 1.
-A solution of 0.1 wt% oxalic acid and 0.05 wt% Triton X 100 gurfactant in water was freshly prepared as etchant. The disk was immersed in the etchant for 50 seconds while the disk was spinning.
The disk was then rinsed sequentially in a 0.05 wt%
Triton X-lOP solution and in distilled water. The disk was subsequently dried by spinning at high rate.
- The disk was then examined by optical microscopy and SEM. It was found ~hat the laser crystallized spots and-tracks were completely etched away and the-boundaries were well defined. The amorphous area was only slightly etched. This etched disk was then ready to be used as a master or as a stamper. -~xample 4 A thin-film about 70 nm in thickness on a glas3 support, of Sb-Sn-In alloy with atomic cbmposition of~ 60%-25~/o~15% was prépared and -:laser-marked às in-Example 1. ~ ~
~5 - ~ A soluti~on--of 1.0 wt~ hydrochloric acid and 0.05 wtZi`Fluorad: FC-99 urfactant in water was ' freshly prepared as etchant.- The dis~ was immersed in~theretchant ~or'240-seconds wh`ile~the disk was ~s'p`inning. :The disk wias then ri~séd^sèquéntially in a 'J30;:0.05-'wtZO~ or`ad~ FC--99;~olution'-ànd inidistilied water.~T3he disk~was subsff~quentl~rdried by spinning at high r^ate. ~ 3 ;~
9?The `di~sk `wa~ the~examined `~by optSic'al~"
microscopy and SEM. It was found that thë`la er crystallized 8pot9 and tracks were completely etché~

WO91/00598 2 ~ ~ 7 0 ~ 7 PCT/US90/03~00 . . ~
. . -15- ~ `
away and the boundaries were well defined. The amorphous area wa~ only slightly etched. This etched disk was then ready to be used as a master or as a stamper.
~E~le $
A thin-film about 70 nm in thickness on a glass support, of Sb-In alloy with atomic composition of 870C/o~20% ~as prepared and laser-marked as in Example 1.
A ~.olution o~ 1.0 wt% hydrochloric acid and O.OS wt% Fluorad FC-99 surfactant in water was freshly prepared as etchant. The disk was immersed in the etchant for 240 seconds while the disk was spinning. The disk was then rinsed sequentially in a 0.05 wt% Fluorad FC-99 solution and in distilled . .
water. The disk was suhsequently dried by spinning at high rate.
The disk was then examined by optical microscopy and SEM. It was ~ound that.the laser crystallized spots and tracks were completely etched away and the boundaries were wel:l defined. The amorphous area was only slightly etched. This etched disk was then ready to be used aæ a master or as a stamper.
xampl~_~ . . ~.. . ... - . .
A thin-film about 70 nm in thickness on a glass support, of Sb-Sn-Ge alloy with atomic composition o~ 63Z-2i7O-i6V/~ was prepared and laser-marked as in E~ample 1. .
A solution:o~ 1.0 wt% hydrochloric acid and 0.05 wt% Fluorad FC-99 surfactant in water was. '.
freshly prepared s etchant.. The disk was immersed in the etchant ~or 360~seco~ds while the disk was spinning. The diak was then rin~ed sequentially in a r - :~ , L ' ' ~ 3 .7 i~ ' J ~-1 . . V~. ~; . .; _ . i J .I. ~
0.05 wtZ Fluorad FC-99 solution and in.distilled ~ I
I

' .

2 Ql ~ 7 0 I r~ ~

water. The disk was subsequently dried by spinning at high rate. The disk was then examined by optical microscopy and SEM. It was found that the laser crystallized spots and tracks were completely etched away and the boundaries were well defined. The amorphous area was only slightly etched. This etched dis~ was then ready to be used as a master os as a stamper.
E~ample 7 A thin-film about 70 nm in thickness on a glass support, of Sb-Sn-Al alloy with atomic composition of 61%-34%-5% was prepared and laser-marked as in Example 1.
A solution of 1.0 wt% hydrochloric acid and 0.05 wt% Fluorad FC-99 surfactant in water was freshly prepared as etchant. The disk was immersed in the etchant for 540 second~ while the disk was spinning. The disk was then rinsed sequentially in a 0.05 wt% Fluorad FC-99 ~olution and in distilled water. The disk was subsequently dried by spinning at high rate.
Thc disk wa~ then examined by optical microæcopy`ànd SEM. It was found that the laser crystallized spots and tracks were completely étched away and the boundaries were well defined. The amorphous area wâ only sli~htly étched. This etched ' disk was then ready to bé u8ed as a master or as a stamper. ~ ~ ~
~ample 8 ' ~' ' ~~~- ` ` ' -~` ~ A thin-film about 70 nm `ln thickness~on a glass support, of Sb-Sn-Zn alloy with atomic composition of 6070-25X-15Z`was preparéd and`
laser-marked as in`Example~l. ` `
`' '~ - ~ ' A ~olution o~ l.0 wt% hydrochloric acid and i ~` 99 surf~actàn't;~in water was : ~' :
. ' ' ' WO 91/~OSg8 2 ~ ~ 7 ~ ~ 7 Pcr/lJS90/03~00 17- ! ., . (, .
freshly prepared as etchant. The disk wàs immersed in the etchant for 600 seconds while the disk was spinning. The disk was then rinsed sequentially in a 0.05 wt% Fluorad FC-99 solution:and in distilled water. The disk wa~ subsequently dried by spinning at high rate.
The disk was then examined by optical microscopy and SEM. It was found that the laser crystallized spot~ and tracks were completely etched away and the boundaries were well defined. The amorphous area was only ~lightly etched. This etched disk was then ready to be used as a master or as a stamper.
~xample 9 A thin-film about 70 nm in thickness on a gla~s support, of Sb Sn-In alloy with atomic composition o~ 60Zo~25~/o - 15%~was prepared and la~er-marked ag in Example 1 and then etched as ln Example 3.
This etched disk was then employed as a stamper and pres~ed against another disk surface which had been coated with a cross-linkable polymer thin.film as described previously. The polymer film was crosslinked via ~V exposure`and the disks were 2~ separated a~ the metal alloy:polymer in~erface. The polymer-coated di~k replicate then had a thin film of the~Sb-Sn-In alloj sputtered onto it to pro~ide ~::reflectivi~y a~d.conductivity ~or subsequent optical -~. micro~copy and}SEM ob~er~ation.;.~'^'c~ `^ ;J
30 ,-.-~ The.:optical and electron microscopy ~
indi~cated:that-the mark~ initially-:laser-written and -~then etched~away ,in:t. the alloy thin film were~-~
~accura~ely reproduced in the polymer layer o~ the : replicate disk. This is:shown~in~:Figure.2 which is a photograph~of~the ~urface of~the replicate di~k.

W~91/00598 .; ; PCT/US90/~3500 2~70~ -18-Example 10 A thin film about 70 nm in thickness on a glass support, of Ge-Te-Ti alloy with atomic composition of 45%-53%-2% was prepared and la~er-marked as in Example 1.
A solution of 1.0 wt% K3Fe(CN)6, 0.25 vol% ~2S04 and 0.025 wt~/o Fluorad FC-99 surfactant in water was freshly prepared as etchant. The disk waQ immersed in the etchant~for l20 seconds while the disk was spinning. The di3k was then rinsed sequentially in a 0.025 wt% Fluorad:FC-99 solution and in distilled water. The disk was subsequently dried by spinning at high rate.
The disk wa~ then exii~mined by optical microscopy and SEM.. It was found that the laser crystallized spots and tracks-were-completely etched away and the boundaries ~ere well defined. The amorphous area was only slightly etched. This e~ched disk was then ready to be used as a master or as a stamper. :
~xample 1~
Ajthin-film about:i70.:nm 7 in thickness.on a glaQ~ support, of Ge-Te-Ti~alloy with-atomic - .
. compo3ition of~45%-53~-2% was:prepared and.-laser-marked as,in Example l.~
: :: A.solution of 3.0 wt%~(NH4)S208, 3,O..
wt% NaO~ and 0.025 wt% FluoradiFC-99 surfactant-.in water was freshly.preparedia~:etchant..~.rf~.The:,disk ~as immerQe~,in:~heletchant fo~ .180:.seconds while the.~.
.'3LO. disk ~a~8plnnlng~ The di~k wa~,then rinsed~
seguentially i~ia O.025;wt% Fluorad~F.C-9.9;solution 3,and.in distilled:water. The~disk(.was subsequently ~dried by.:~pinning.at.,high.rate. ..,i~ m~
~ -Theldi~k was then ~amined.;byi~.optical:, microscopy and SE~. It wa~ found that the laser : :
'' . ~, '' ' ' ' .

WOgl/00598 2 0 ~ r¢ ~ ~ 7 PC~/US~0/03~00 ~, . . . .

crystallized spots and tracks were completely etched away and the boundaries were wPll defined. The amorphous area was only ~lightly etched. This e~ched disk wat3 then ready to be used as a mastter or as a 5 stamper.
~xample lX
A thin--f ilm about 70 nm in thickaless on a glass support, of Ge--Te Ti alloy with atomic composition o~ 45"Z-53/.-2% wa~ prepared and 10. laser-marked as-in Example 1..
A olu~ion of 3.0 wt% Na2Cr207, 3.0 wtn/o NaOH and 0.025 wt% Fluorad FC-99 ~urfactant in water was ~reshly prepared a~ etchant. The disk was immersed in the etchant ~or 180 t~teconds while the lS di3~ wa~ sp;~ning. The tisk was the~- rin~ted sequen~ially in a 0.025 wt% Fluor d FC-99 solution and in distilled water. The disk was subseque~tly dried by ~tpinning at high rate.
The disk was then examined by optical microscopy and S~M. It wat3 fou~d that the lager crystallized spots and:tracks were completely etched away and the boundaries were well defi~ed.: The amorphous area was only ~lightly etched.-~This!etched disk wal then ready to.be:u3ed as a ma?ter or as? a .~25 stamper.
.. . ~ . .. .. ..

3~ -` L: ;~li. `.`, `, . :` :7 ~ 3~5~,3,~1 r ,~ r, ?~ ,y'~,-3,r~ 'jO~ J~ r;:~ r~;~ r~'Tj~3'' 2rC.

Claims (7)

We claim:

1. A method for forming a master for making replicate optical elements, said method comprising the steps of:
a) focusing an information modulated energy beam on a phase-change optical recording layer so as to form a pattern of two different phases in said layer corresponding to said information; and b) selectively etching away one of said two different phases so as to form a relief pattern corresponding to said information.

2. A method according to claim 1 wherein said two phases are the amorphous and the crystalline phases and the crystalline phase is selectively etched away in step b).

3. A method according to claim 1 wherein said energy beam is a laser beam.

4. A method according to claim 1 wherein said optical recording layer comprises an antimony-tin-indium alloy.

5. A method for forming a stamper for making replicate optical elements, said method comprising the steps of:
a) focusing an information modulated energy beam on a phase-change optical recording layer so as to form a pattern of two different phases in said layer corresponding to said information; and b) selectively etching away one of said two different phases so as to form a relief pattern corresponding to said information;
c) conductively coating the master produced in step b) and electroplating said conductive coating with nickel; and d) polishing and peeling the nickel layer formed in step c) from the surface of said master.

6. A master for making replicate optical elements, said master comprising a support having thereon a phase-change optical recording layer having a relief pattern corresponding to the information that is to be transferred to said optical element.

7. A method for making a replicate optical element comprising the steps of:
a) focusing an information modulated energy beam on a phase-change optical recording layer so as to form a pattern of two different phases in said layer corresponding to said information; and b) selectively etching away one of said two different phases so as to form a relief pattern corresponding to said information;
c) pressing the master formed in step b) into a polymer layer and photopolymerizing said polymer layer so form a replicate of said relief pattern.